This invention relates to equalizing tire pressure in dual tires and allowing convenient visual determination of that pressure. It is particularly useful in connection with dual tires commonly used on trucks.
In my U.S. Pat. No. 2,789,617 I describe a pressure equalizing valve in which two chambers, each in communication with one of the tires, are connected to each other by two passages. Each passage is sealed at one end by a valve member connected to a diaphragm which is acted upon by the pressure in that chamber. Upon inflation through the single fitting connected to one of the chambers, the diaphragm in that chamber is lifted, allowing air to move through one of the passages to the other chamber. When the pressure in the second chamber reaches a certain value, the valve member and diaphragm in that chamber will also move to an open position, and the chambers will be in communication through both passages.
In my U.S. Pat. No. 3,079,974 I describe a device in which each tire is connected to a separate chamber within a valve, and each chamber has its own inflation fitting. The chambers are connected by a long passage sealed at each end with a diaphragm responsive to the pressure existing in the tire connected to that chamber.
In Spicer U.S. Pat. No. 1,882,455 a single inflation fitting feeds two tire fittings, the passage of one tire fitting being sealed when the pressure falls to a certain cutoff value.
Denmire U.S. Pat. No. 1,849,139 discloses a tire pressure indicator connected to a pressure equalizing valve through a long tube and a pressure linkage system mounted on the wheel hub.